1. Field of the Invention
The present invention relates to an audio correcting apparatus in which the level of sound output from a piece of equipment, such as a television set or an audio apparatus, is corrected in response to ambient noise or the like.
2. Description of the Related Art
In general, when sudden noise is generated while a person is listening to sound from a television set or the like in the home, it becomes difficult for the person to hear the sound clearly. For example, when people in the vicinity speak or make some kind of noise, or there is some external noise, such as noise from a car, it becomes difficult for the person to listen clearly to what the person is watching or listening to. In such a case, in general, the person will then naturally increase the volume. To actually increase the volume after the sudden generation of noise or the like, a certain amount of time is required during which the person may fail to hear some of the sound.
As an example of the related art which enables a person to listen to sound even if ambient noise is generated, an in-vehicle speech correcting apparatus (for a car navigation apparatus) using volume correcting technology based on acoustic theory is known (see, for example, Japanese Unexamined Patent Application Publication No. 11-166835, pages 3 to 7, FIGS. 1 to 10). This speech correcting apparatus includes a microphone provided at a listening position and performs gain correction on output sound in response to a noise level at the listening position. This enables the user of the apparatus to always be able to hear that which is represented by the sound, even if the noise level changes.
For the above speech correcting apparatus, the microphone must be provided at a position where the user listens to the sound. When considering the inside of the vehicle, in the case in which the user sits in the driver's seat, the listening position is almost fixed. Accordingly, the microphone may be actually provided at the listening position. However, when considering the case of listening to sound which is output from a television set or an audio apparatus for household use, the user will listen to the sound at his or her chosen position in a room. Accordingly, it is almost impossible to provide the microphone at that position since the required wiring is complicated. Although it is possible for the microphone to be mounted on part of the housing of the television set or the audio apparatus, it is difficult to employ such a solution because measurement of a sound pressure level at the listening position is essential for accurate volume adjustment based on volume correcting technology.